Spark plugs and the like



Aug. 18, 1959 ENGEL 2,900,547

SPARK PLUGS AND THE LIKE Filed Aug. 5, 1956 I I I /z 2/ a c w I A TTOKIVEYS United States This invention relates in general to electrical mechanism for igniting combustible gases and, more particularly, the invention relates to an ignitor or spark plug for internal combustion engines.

The embodiments of the invention described herein relate to spark plugs for internal combustion engines used in passenger-type vehicles. As the description proceeds, however, it will be appreciated that the invention is applicable for internal combustion engines used in a wide variety of circumstances, for example, in aircraft, trucks, tractors, air compressors, auxiliary power units, earth moving equipment and other like engine-powered equipment.

The invention is of a nature as to have highly desirable advantages from several standpoints. For example, as to consumers such as the ordinary automobile owner and the fleet operator, the invention provides spark plugs which reduce the cost of operation by effecting very substantial savings in cost of fuel and in fuel consumption, While at the same time giving highly improved engine performance and continuity of operation for long periods of time. From the standpoint of health and smoke nuisance, the invention isof special importance as it provides for highly improved combustion which cuts down on carbon monoxide and other obnoxious exhaust products and, therefore, it is important to highly travelled municipalities and to the garaging problems connected with taxi, bus, truck and other large-scale automotive operations. Additionally, the invention is important to vehicle and engine manufacturers because a fewer number of heat rangetypes of spark plugs is required so that warehousing and dealers stock problems are simplified.

As is well known, a spark plug comprises essentially two electrodes disposed within an engine cylinder so as to be in close association with the gaseous mixture of fuel and air. A voltage on the electrodes causes a spark or a passage of electric current therebetween resulting in the ignition or explosion of the gaseous mixture, the expansion of which exerts a force on the pistons. Simply stated, the ideal result desired in the ignition process is to cause the burning or exploding of all the fuel in the cylinder so. that a greater proportion of the energy released in the burning is available to do work on the pistons. v Heretofore, in aneifort to increase the degree of fuel burning, agents suchas lead compounds have been added to gasoline to make the so-called high test or anti-knock fuels. While such fuels have been an improvement and, indeed, are almost an absolute necessity in modern high compression engines, they are not without disadvantages. For example, the higher test gasolines are considerably more expensive than the so-called regular gasolines. In addition, the lead compounds in the fuel have a deleterious effect on the engine, for example, in attacking the cylinder walls, valves and the plugs themselves, which can lead to a reduction in the amount of fuel ignited. Lead fouling causesloss of engine power and performatent .O

ance, the correction of which requires expensive engine overhaul.

Other efforts to increase the efliciency of fuel burning have been in connection with the design of the spark plugs themselves, for example, by increasing the gap Width or spacing between the electrodes. In modern day cars, the gap width or spacing between the electrodes is in the order of 0.035" as compared with gap widths of the order of 0.020" in cars of bygone years. The increase of gap width has required an increase in the voltage level to cause breakdown, and the higher voltage levels sometimes cause undesirable electrode sputtering or disintegration and changes in gap width which, if large enough, may cause the plug to fail to spark over. This disadvantage has-been attacked by incorporating a re sistor in the voltage supply circuit which limits the available current on discharge. Other efiorts to improve spark plug performance have been concerned with the shape or the number of electrodes. However, the electrode material has been almost exclusively platinum or alloys of nickel. Other changes have concerned themselves with improvements in heat transfer, in reducing leakage, and in the size of plugs and the like.

The present invention provides for a very substantial improvement in fuel burning by constructing the elec trodes so that considerably more energy is available to effect the chemical reaction necessary for combustion. The invention concerns itself with electrode material and the surfacing thereon. I have found that by using an electrode of conducting material having an insulating surface, high beneficial if not startling results are obtained. While on first consideration it might be thought that an insulating surface on a conductor would render a spark plug inoperative, I have found that not to be the case. Preferably, the invention proposes an electrode made of aluminum which has an integral surface of aluminum oxide. Other materials and surfaces are also useful and these will be described hereinafter.

In the following paragraphs I have set out certain advantages, objects and features of the invention which will serve to illustrate the substantial advance in the art obtained by the present invention.

One of the principal advantages of the invention is in the realization of substantial savings in fuel. For example, With the spark plugs of the invention, a passenger car can be operated with regular rather than high test fuels and without pinging or knocking and with increased engine performance as Well. The foregoing is effective even with the modern high compression engine. Considen'ng the fact that high test fuels cost about 10% more than regular fuels, it will be appreciated that fuel costs with my spark plugs can be substantially reduced. In deed, the spark plugs of the invention permit an engine to perform entirely satisfactorily with the so-called thirdrate fuels, whose cost is about 20% less than the premium or high test fuels.

7 Further, in connection with savings in fuel costs, the spark plugs of the invention permit a much leaner mixture, i.e., less gasoline to air, to be used.. Thus, the actual consumption of gasoline per mile of operation is decreased or, stated in another way, the invention increases the mileage per gallon of fuel. For example, in tests under city driving conditions, an average of 11.6 miles per gallon was obtained with high test fuel and conventional plugs whereas, with the plugs of the invention, an average of 15.7 miles per gallon was obtained. An increase of about 35%. As a further illustration of the effectiveness of the invention, it might be pointed out that the latter test was carried out with low-grade rater than high test fuel! Another principal advantage of the invention resides in substantial savings realized by a reduction in the cost of engine maintenance. of the invention, an engine can be idled at from 25 to 30% less r.p.m. than an engine having conventional plugs. It is estimated that idling comprises about 25% of normal engine operation for passenger cars and, there fore, it will be appreciated that engine wear, hence likelihood of repair and overhaul, is reduced. Furthermore, the over-all engine life is consequently increased. Since with my plugs the engine is running at a lower r.p.m. during idling, it will be apparent that less fuel is consumed.

As mentioned heretofore, with the spark plugs of the invention, it is not necessary to use high test or leaded fuel. Therefore, there is no possibility of lead fouling and consequently, there is no danger of expensive maintenance or overhaul to correct the damages done by such fouling. Further, in connection with engine maintenance, the present invention is effective in promoting For example, with the plugs a very high degree of burning of the fuel and, therefore,

the danger due to carbon buildup on engine parts is practically eliminated. Carbon buildup, of course, results in loss of engine power, poor engine starting and performance, sticking valves and the like and, of course, these are only corrected by engine overhaul.

Another advantage of the spark plugs of the present invention resides in their ability to increase power output. For example, dynamometer tests have shown an engine equipped with my plugs to have an increased power output from 10 to 30% depending upon engine speed, as compared to its power output with conventional plugs. Thus, with my plugs, an engine has greater dependability in the sense of more power being available for acceleration, hill climbing, load carrying and the like.

Another advantage of the present invention is in the economies effected because of the quality of the plugs themselves. For example, the plugs of the present invention have an effective operating life in an engine which is almost double that of conventional plugs. Furthermore, the electrodes of my plugs are highly resistant to sputtering or erosion and in certain instances there is no need for gap adjustment or cleaning throughout useful operating life.

Certain other advantages and features will be apparent from the following description and drawings wherein:

Figure l is an elevational view partially in section showing the invention as applied to one type of spark P Figure 2 is an elevational view partially in section showing the invention as applied to another type of spark plug; and

Figure 3 is an isometric view of a typical electrode for use with the plugs of Figures 1 and 2. V

1 In Figure l I have shown a spark plug P which, in general, is constructed in the usual form comprising a metal shell 1, a core ofinsulating material 2 and a terminal 3, the shell having an annular-shaped lower extension 4. A ground electrode 6, which is usually in rod or bar-like form, is secured to the portion 4. The core 2 extends down into the shell and terminates within the extension 4 as indicated at 10. The core is hollow and mounts a center electrode 11 and extends up through the core where it is connected to the terminal 3.

The width or distance .9 between the electrodes 6 and 11 is known as the spark gap and, in many instances, the ground electrode 6 is the anode and the center electrode 11 is the cathode. As will be noted, the lower extension 4 of the plug has external threads 12 by means of which the plug is fixed in the engine block so that the spark gap s is within the cylinder or combustion chamber of the engine. In the usual ignition system for automotive vehicles, a voltage is applied to the electrodes which causes a spark between the two, which results in ignition of the fuel in the combustion chamber.

As mentioned heretofore, the invention herein is concerned with electrode material, particularly the material of the cathode and the surface thereon. The cathodes of my invention are formed from a good electrical conductor and have an insulating surface which is preferably disposed such that it forms at least a portion of one end of the spark gap. For instance, I prefer the basis metal for the electrode 11 to be made of aluminum or certain of its alloys, the tip end of which has a surface of aluminum oxide 13, as is illustrated in Figures 1 and 3. The outer electrode or anode 6 is made of ordinary electrode material which is usually nickel and 5% manganese.

There are several commercial grades of aluminum and its alloys available. For example, I have found that any one of the following may be used with highly satisfactory results: 2S, 3-8, 52-3 and 61-8. In considering cathode materials, I have found that aluminum alloys which contain zinc do not permit suificiently thick surfaces to be obtained by anodizing. Aluminum alloys containing copper also restrict the thickness of the surface obtainable by anodizing, although these alloys are better than the zinc alloys in this respect.

As mentioned above, the modern day spark plug uses the outer electrode as the anode while the inner electrode is used as the cathode. In some instances, however, the polarity of the electrodes has been reversed. If it is desired to construct a plug for such operation, then the center electrode 11 is made of the usual electrode material while the outer electrode is made of aluminum with its tip portion having an aluminum oxide surface.

In Figure 2 I have shown the invention as used in a so-called surface gap spark plug which is discolsed in the Parkin Patent No. 1,962,669. It will be observed that this structure differs from that described in that the outer electrode is removed and the end face 15 of the hollow core 16 is interposed between the center electrode 20 and the shell 21. The gap between the center electrode and the shell is annular andcomprises the outer surface of the core 15 and the air space 22. The shell 21 serves as the ground electrode or anode and is made of nickel alloy, while the center electrode or cathode 20 is made of aluminum and has an aluminum oxide surface 23. In the event the polarity of the electrodes is to be reversed, then the center electrode is made of nickel alloy while the shell may be made of aluminum and have an oxide coating on the tip 24. Alternatively, the shell may be made of steel with an aluminum insert on the tip. i

Preferably the oxide surface for the above-mentioned electrodes is obtained by standard sulfuric acid anodizing and should be at least 0.001 thick. The preferred thickness is in the order of 0.004, as I have found this to be conducive to very good electrode characteristics. It might be noted that electrodes with the thinner surfaces, while giving desired improvements in combustion of the gases, tend to have a somewhat shorter operating life. While other means are available for obtaining the oxide surface, I prefer that anodizing be used because the surface or film is integral or molecularly bonded with the basis metal. I have found that an oxide surface which is integral or very firmly bonded to the basis metal is important, particularly from the standpoint of long operating life for the electrode. If other means are used to provide the surfacing, it is important that the adherence characteristics to the basis metal should be of similar ten acity to that of the integral film obtained by anodizing.

It might be noted here that the 4 mil surface obtained by anodizing is very hard, for example, having Knoop hardness numbers in the order of: outer zone, middle zone, 3000; and inner zone, 5000. p

I have found that in a spark plug having a cathode constructed as described, the gap width or distance between electrodes can be between 0.050"0.080" which is considerably more than that now obtained in conventional plugs. Further, I have found that the most effective results are obtained when the cathode rather than the anode is of the kind mentioned. Also, there is some improvement in performance where the anode as well as the cathode is made of aluminum and has an oxide surface, although from the commercial standpoint, the extra expense may not justify its use.

In the foregoing discussion, it was pointed out that the preferred electrode comprises aluminum with an aluminum oxide surface; however, other basis metals which are capable of having an integral surface of their own oxide may be used. For example, I have used titanium, magnesium and silicon and found these to give satisfactory results. However, with these metals the following should be observed. It is difficult to obtain oxide surfaces of titanium and magnesium which are as thick as those obtainable with aluminum. Thus, plugs having electrodes made from these metals might be expected to have a shorter operating life than the aluminum electrodes, although otherwise performance characteristics are satisfactory. Titanium and its oxide coating give satisfactory results comparable to that of aluminum. However, plugs having electrodes made of this metal should not be consistently used with high test or leaded gas as the silicon dioxide has a tendency to be attacked thereby.

Before proceeding, it might be noted that one of the principal advantages to the use of an electrode with a surface of aluminum oxide is that fewer heat range types of plugs are required. In the ignition process it is necessary that the electrodes rapidly cool after combustion in order not to hold sufficient heat to cause the gaseous mixture to ignite prior to the application of the external voltage. In conventional plugs this is compensated for by varying the length of the portion 4 so that sufficient metal is present to conduct away the heat. Since different, engines run hotter or cooler than others, and generally engine temperature may vary geographically, a variety of heat ranges is necessary in conventional plugs. With my electrodes, however, fewer varieties of the length of the portion 4 or fewer heat ranges are required because the aluminum oxide surface itself cools very rapidly. For example, aluminum oxide has the highest emissivity value (heat radiation) next to a black body.

Recalling to mind the several results or advantages of the invention which have been heretofore mentioned, it is desired to comment on certain aspects of the invention with relation to the manner in which these results are brought about.

With relation to the increased burning of fuel and the advantages resulting therefrom: There are several theories regarding the mechanism of ignition and the complete theoretical operation is not completely understood. However, it is more or less generally agreed that energy must be supplied in order to effect the chemical action necessary for combustion. The present invention supplies such energy in certain ways in more abundance than is possible in the conventional plugs and in other ways, supplies energy in a manner which is not possible at all in conventional plugs.

My plugs attack the problem of burning from the standpoint of increased molecular activation or ionization which, incidentally, is a factor which has been discounted by the art as being a vehicle for improving the combustion process. My plugs give a considerably higher degree of gas ionization than is possible in the conventional plugs and, therefore, an increased level of energy from this source is available for use in the combustion 6 process. Initially, the ionzation is due, I believe, to the intensity or distortion of the electric field set up by the electrode surface coating. Subsequently the ionization is measurably increased because my surface coating, I believe, acts more nearly like a capacitor than the electrodes of conventional plugs in the sense of holding back the actual discharge or electron emission so that its energy is instantaneously released in the gap rather than being dribbled thereto and/or in the sense of giving high frequency oscillations to the discharge which gives added stimulus to the dissociation of gas atoms. Additionally, the oxide coating on the electrode is a dielectric and I believe that certain electron movement therein associated with the phenomenon of sparking may make thermal energy available for the ignition process.

With respect to the long life of the spark plugs of the invention, the oxide coating on the electrodes of the invention is very hard in the mechanical sense and to this I attribute the fact that the electrode is highly resistant to the erosive effects of the gases.

Before closing, it should be pointed out that in using the plugs of the invention in engines of the passenger car type, the timing should be set ahead about 9 BTDC.

'In other words, with my plugs, the voltage is applied earlier than is the case with conventional plugs where the timing is set about 2 BTDC.

I claim:

1. In a spark plug, a pair of electrodes in juxtaposition with one another to form a spark gap, one of the electrodes being formed of electrically conductive material and having a molecularly bonded insulating surface forming a portion of one end of the spark gap.

2. In a spark plug, a pair of electrodes in juxtaposition with one another to form a spark gap, one of the electrodes being made of metal and having an integral surface formed of the oxide of the metal, the surface forming a portion of one end of the spark gap.

3. In a spark plug, a pair of electrodes in juxtaposition with one another to form a spark gap, one of the electrodes being composed of metal from the class consisitng of aluminum, magnesium, titanium and silicon and the electrode having an integral surface formed of its own oxide, the surface forming a portion of one end of the spark gap.

4. In a spark plug, a pair of electrodes in juxtaposition with one another to form a spark gap, one of the electrodes being made of aluminum and having an anodized surface thereon, the surface forming a portion of one end of the spark gap.

5. In a spark plug, a pair of electrodes in juxtaposition with one another to form a spark gap, one of the electrodes being formed of electrically conductive material and having a molecularly bonded dielectric surface Whose thickness is greater than approximately 0.001", the surface forming a portion of one end of the spark gap.

References Cited in the file of this patent UNITED STATES PATENTS 1,152,272 Boas Aug. 31, 1915 1,361,967 Capley Dec. 14, 1920 1,491,752 Richey Apr. 22, 1924 1,754,796 McElroy Apr. 15, 1930 1,775,007 Von Lepel Sept. 2, 1930 2,391,456 Hensel Dec. 25, 1945 2,603,200 Feichter July 15, 1952 2,760,099 Suter Aug. 21, 1956 FOREIGN PATENTS 922,384 Germany Jan. 13, 1955 

